Nutrient uptake is by the fine microscopic roots which are diminished when the roots don't get enough oxygen from poor drainage which you would have in clay. I think anything you will do will only be a temporary fix unless you can get the tree into a better soil. Is it too big to move at this point?

Hmm, I just remembered. I believe Acer Ginalla produce tap roots so I suppose transplanting would be too hard.

You may have to fertilize it and hope for the best. After your leaves start to turn in Autumn you should add a micronutrient supplement or a very low nitrogen fertilizer that has the full spectrum of appropriate nutrients.

You will get some root growth in the fall hopefully while the ground is still warm and MAYBE get enough nutrient uptake. You might want to consult a arborist on this one.

I can't say for you, but at our home sit atop a bank that was created when a road was cut in front of our house into a clay hill. As such, much of our yard is sloped clay that was originally a clay subsoil, and is extremely poor in nutrients. In addition, our clay is a Ultisol, which is low in nutrients to begin with, and those nutrients that are present are in the top few inches. This may be what is happening with your site (resulting in the chlorosis), but various clays are often brought to a development site as fills. Either way, the only thing you can do that I know of, is to add nutrients and work on building organic matter. I use fertilizers that contain additional minor to micro nutrients. In addition I use Milorganite which is derived from treated sanitary sewage of Milwaukee (yes there is some smell, but it dissipates in a day or two at most). Milorganite has iron added, but should also contain other nutrients as well. I know is the grass, shrubs and tree sure respond to it in a positive way. I also try to manage our lawn so as to encourage the grass roots to sink deeper into the clay, resulting in better retention of nutrients, better aerated soil, and more organic matter. But we will probable both be adding nutrients for some time to come.

Is Iron/Magnesium deficiency common in your area?? A foliar application of Epsom salts (1tbsp per gallon of water, spray to drip) would rule Mag. out if a change was not seen...Mag. is very soluble and foliar applications are common for some growers. This wont solve the problem, but could determine/rule out a nutrient.
Keep in mind it could also be manganese..Acers in general have much higher needs of manganese than iron (based on tissue analysis) and a lack of would look very similar.

This is a follow-up message. We had the IV treatment done a year ago. It helped quite a bit. I'd say the tree looks 85-90% better. Since it looks so much better, we did not give it a second IV treatment this season (2009). Instead, we gave it iron via fertilizer this season.